Time zones Introduction
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The document discusses the concept of time zones, primarily based on Greenwich Mean Time (GMT) which is calculated from the prime meridian in Greenwich, England. It explains how local times are adjusted in relation to GMT for various locations and outlines the Earth’s rotation and revolution in relation to measuring time. Additionally, it mentions the effects of Daylight Saving Time and provides examples of calculating time differences between various cities.
![If it is 7:08am
[07:08 hrs]
hours in London
…
Map
… what time is
it in Sydney?
Sydney = London + 10hr [East]
= 07:08 + 10hr
= 17:08 = 5:08 pm](https://image.slidesharecdn.com/timezonesintro-131104181832-phpapp02/85/Time-zones-Introduction-11-320.jpg)
![If it is 10:20am
[10:20 hrs]
hours in Sydney …
… what time is
it in Honolulu?
Honolulu = Sydney - 20hr [West]
= 10:20 - 20hr
= -10:20 + 24:00 = 14:20 yesterday
= 2:20 pm yesterday
Map](https://image.slidesharecdn.com/timezonesintro-131104181832-phpapp02/85/Time-zones-Introduction-12-320.jpg)
Time zones Introduction
- 2. All time is measured from Greenwich a suburb of London in England. The zero degree longitude line or the Prime Meridian passes through Greenwich. Greenwich Mean Time (GMT) is the time it is in Greenwich. Greenwich was chosen as a lot of the world’s sea charts were being drawn up in England at that time.
- 3. Time zones are calculated in relation to GMT. Greenwich Mean Time For locations to our east we add time. For locations to our west we subtract time. Perth = Adelaide – 1hr 30min = 9am - 1hr 30min = 7:30 am Perth 7:30am Map Adelaide 9am
- 4. DURING DAYLIGHT SAVING TIMES IN AUSTRALIA, TIMES CHANGE SLIGHTLY Note: Times are still calculated in relation to GMT times.
- 5. 1 revolution of Earth = 365.25 days 6 hours x 4 years = Leap year & we catch up 1 rotation of Earth = 24 hours Circle = 360° 360° /24 = 15° = 1 hour Earth rotates 15° each hour At the equator Earth ≈ 24,900 miles = 1037.5 miles in an hour L North Pole 15° e in s of n Lo g d itu e
- 7. UTC = GMT UTC = Coordinated Universal Time 11.23am Gold Coast Time Los Angeles is 18 hours behind Gold Coast and is still the day before.
- 8. Los Angeles is 18 hours before G.C. Time 14.33-18 = 12-4 = 8.33pm New York is 15 hours before G.C. Time i.e. 1433-15=-1 =0033 -1 = 2333hrs By this photo, you can see more of the world is now into the next day of the calendar. You can see that it has just passed midnight in Bolivia. i.e. 14.33pm – 14hrs = 0033hrs
- 9. 1803 Gold Coast Time – GMT +10
- 10. You can see here, that it is about 10pm in Queensland. In this hour, the whole Earth is on the same day. Once it hits 11pm, (Qld time), 15 degrees west of the International dateline is in the next day.
- 11. If it is 7:08am [07:08 hrs] hours in London … Map … what time is it in Sydney? Sydney = London + 10hr [East] = 07:08 + 10hr = 17:08 = 5:08 pm
- 12. If it is 10:20am [10:20 hrs] hours in Sydney … … what time is it in Honolulu? Honolulu = Sydney - 20hr [West] = 10:20 - 20hr = -10:20 + 24:00 = 14:20 yesterday = 2:20 pm yesterday Map
- 13. When crossing the International Date Line… •going east – subtract (24 hours) one day •going west – add (24hrs) one day If we look at two island nations that are about 900 kms apart. Map